“She has been saying lately that she thinks I am quote, unquote ‘not qualified’ to be president,” Sanders said at Temple University. “I don’t believe that she is qualified ... if she is, through, her super-PAC, taking tens of millions of dollars in special interests funds.”

"I don't think that you are 'qualified' if you get $15 million from Wall Street through your super-PAC. I don't think you are 'qualified' if you have voted for the disastrous war in Iraq. I don't think you are 'qualified' if you have supported virtually every disastrous trade agreement," the Vermont senator added.

Clinton's campaign denies that the former secretary of State called Sanders "unqualified" for the presidency. She dodged several times during a Wednesday interview on MSNBC when asked if she thought Sanders was qualified for the presidency.

Instead, she pointed to Sanders's remarks in a New York Daily News interview, saying it "raised a lot of really serious questions" about the independent senator's qualifications on several issues, namely going after "big banks." "I think he hadn't done his homework," she said.

The remarks highlight escalating rhetoric between the two Democratic hopefuls as Clinton looks to defend turf in New York ahead of the state's April 19 primary, while Sanders hopes to keep up momentum following wins in several recent states, including most recently Wisconsin.

Clinton has been hitting Sanders on his Democratic credentials, saying in a Politico podcast released Wednesday that she’s “not even sure” Sanders is a Democrat. She later said during a television appearance that he "himself doesn't consider himself to be a Democrat."

Sanders said late Wednesday that "Secretary Clinton appears to be getting a little nervous" amid his riff claiming Clinton is not qualified for the White House, prompting backlash from her campaign:

Hillary Clinton did not say Bernie Sanders was 'not qualified.' But he has now - absurdly - said it about her. This is a new low.